Are there limits on how human beings can legitimately treat non-human animals? Or can we treat them just any way we please? If there are limits, what are they? Are they sufficiently strong, as some people supp ose, to lead us to be vegetarians and to seriously curtail, if not eliminate, our use of non-human animals in `scientific' experiments designed to benefit us? To fully appreciate this question let me contrast it with two different ones: Are there limits on how we can legitimately treat rocks? And: are there limits on how we can legitima tely treat other human beings? The an swer to th e first ques tion is pre suma bly `No.' Well, that's not q uite right. There are som e limits on what w e can le gitimate ly do with or to rocks. If Paula has a pet rock, then Susan can't justifiably take it away or smash it with a sledge hammer. After all it is Paula's rock.